This invention relates to the field of power driven rotary tools and in particular to a power drive unit that can receive and operate tools designed for operation by hand such as ordinary hand operated screwdrivers.
Prior art devices relevant to this invention of which the inventor is aware include those described and shown in the following United States patents.
U.S. Pat. No. 4,949,463 discloses a mechanism for connection to a regular electric drill which converts rotary motion of the drill to reciprocating motion of an eccentric strut to which a saw blade may be attached.
U.S. Pat. No. 4,480,512 discloses a screwdriver which can be used manually as well as connected to a power drill for powered operation. The handle has a recess in which a coupling shaft is received for movement into such recess for manual use of the screwdriver and out from such recess for gripping by the chuck of a power drill for operation in the power mode.
U.S. Pat. No. 4,437,365 also discloses a screwdriver which can be used manually as well as connected to a power drill for powered operation. An adapter fitting which includes a short shaft having an angular cross-sectional configuration, is received at one end in the chuck of a power drill and at the other end in an angular cross-section recess in the handle of the screwdriver opening to its outer end.
U.S. Pat. No. 4,161,242 discloses a power driven drill and screwdriver having two clutches movable to provide either a positive drive connection between the motor and tool element or a drive connection that can be established and interrupted at will by the person operating the tool.
U.S. Pat. No. 2,457,829 discloses a power driven hand hacksaw, which includes a rotatable drive shaft having an endless groove in the form of a double helix wherein the grooved turns of each helix intersect. An insert lug received in such endless double helix groove is moved forward to one end of the grooved drive shaft as it rotates, then backward to the other end of the grooved drive shaft, continuing such back and forth reciprocating motion as the drive shaft continues to rotate in the same direction of rotation. The hack saw blade is secured to the insert lug and thereby moved back and forth in a sawing operation as the grooved drive shaft is rotated.
U.S. Pat. No. 1,808,228 discloses an attachment for electric drills which includes a rotating barrel cam that guides a cam follower to impart reciprocating motion to a tool such as a saw blade, a file and the like.
The present invention is an improvement over prior art devices in that it enables using a power tool to drive rotatable hand tools such as ordinary screwdrivers, drill bits that are normally used with a hand operated brace, and other rotatable hand tools which have a working end and an opposite end too large to be received in the chuck of prior art power tools such as power drills.